And in some cases you don't even need to corner the market - just abuse your adversaries' psychology. For example, Canada, was sending tons of PPE to China in February. [1]

This turned out to be an awful decision and Canada was caught in a terrible shortage weeks later. China gladly sold PPE to Canada though.

[1] https://www.canada.ca/en/global-affairs/news/2020/02/canada-...